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Minneapolis overhauls network of emergency warning sirens

Minneapolis is in the process of replacing each of its 30 existing emergency sirens and adding 12 more in a complete overhaul of its emergency warning system.

The first phase of the project is expected to be operational by Jan. 1, but it only addresses sirens outside of Downtown.

Bruel and Kjaer, a Danish sound engineering company, is finishing up a 3D mapping study of Downtown that will be used to in conjunction with an acoustic software program to determine how to redo Downtown's emergency warning system. That project will probably not be finished until later in 2014.

Currently the city does not meet the Federal Emergency Management Agency's (FEMA) sound coverage guidelines, and about half of Minnapolis' emergency sirens are mounted on school or private property, making repairs difficult. After the first phase is complete all sirens outside of Downtown will be mounted on 45-foot poles and will be located in the city's right-of-way, according to Minneapolis Energy Manager Brian Millberg.

The first phase of the project was funded by a $552,000 grant from FEMA and $270,000 from the city. The second phase's total budget won't be known until the acoustic 3D mapping analysis is complete.

Milberg said Downtown is tougher to address because its density and abundance of tall buildings.

"It'll take some time to figure out which siren to use, how many we need and where to put them," he said. "Outside of Downtown our crews can do three a day because it's much more simple."

Downtown's sirens will be 10-20 decibels quieter than regular emergency sirens and could be mounted on skyways, light poles or government buildings.